Chrome talks to Play to install WebAPKs.

chrome/android/java/src/org/chromium/chrome/browser/init/ProcessInitializationHandler.java

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.init;
 
 import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
 import android.view.View;
@@ skipping 17 matching lines @@
 import org.chromium.chrome.browser.identity.UniqueIdentificationGeneratorFactory;
 import org.chromium.chrome.browser.identity.UuidBasedUniqueIdentificationGenerator;
 import org.chromium.chrome.browser.invalidation.UniqueIdInvalidationClientNameGenerator;
 import org.chromium.chrome.browser.multiwindow.MultiWindowUtils;
 import org.chromium.chrome.browser.net.spdyproxy.DataReductionProxySettings;
 import org.chromium.chrome.browser.preferences.PrefServiceBridge;
 import org.chromium.chrome.browser.rlz.RevenueStats;
 import org.chromium.chrome.browser.services.AccountsChangedReceiver;
 import org.chromium.chrome.browser.services.GoogleServicesManager;
 import org.chromium.chrome.browser.sync.SyncController;
+import org.chromium.chrome.browser.webapps.WebApkInstaller;
 import org.chromium.components.signin.AccountManagerHelper;
 import org.chromium.content.common.ContentSwitches;
 import org.chromium.printing.PrintDocumentAdapterWrapper;
 import org.chromium.printing.PrintingControllerImpl;
 import org.chromium.ui.UiUtils;
 
 /**
  * Handles the initialization dependences of the browser process.  This is meant to handle the
  * initialization that is not tied to any particular Activity, and the logic that should only be
  * triggered a single time for the lifetime of the browser process.
@@ skipping 124 matching lines @@
      * Performs the post native initialization.
      */
     protected void handlePostNativeInitialization() {
         final ChromeApplication application =
                 (ChromeApplication) ContextUtils.getApplicationContext();
 
         DataReductionProxySettings.reconcileDataReductionProxyEnabledState(application);
         ChromeActivitySessionTracker.getInstance().initializeWithNative();
         ChromeApplication.removeSessionCookies();
         AppBannerManager.setAppDetailsDelegate(application.createAppDetailsDelegate());
+        WebApkInstaller.setWebApkInstallClientDelegate(
+                application.createWebApkInstallClientDelegate());
         ChromeLifetimeController.initialize();
 
         PrefServiceBridge.getInstance().migratePreferences(application);
     }
 
     /**
      * Initializes the deferred startup tasks that should only be triggered once per browser process
      * lifetime.
      */
     public final void initializeDeferredStartupTasks() {
@@ skipping 59 matching lines @@
 
                 if (ApiCompatibilityUtils.isPrintingSupported()) {
                     String errorText = application.getResources().getString(
                             R.string.error_printing_failed);
                     PrintingControllerImpl.create(new PrintDocumentAdapterWrapper(), errorText);
                 }
             }
         });
     }
 }